Rule Definition
Python Exceptions accept all arguments passed to them being stored in the .args attribute as a tuple. Various libraries and parts of Python rely on this behaviour. To prevent source of errors and unexpected behaviour, avoid inconsistent initialization when subclassing a new exception by passing the same number of arguments to the parent __init__ call.

Remediation
Initialize parent exception class with the same number of parameters.

Violation Code Sample

>>> class CustomError(Exception):
>>>     def __init__(self, message, status):
>>>     self.message = message
>>>     self.status = status

Fixed Code Sample

>>> class CustomError(Exception):
>>>     def __init__(self, message, status):
>>>     self.message = message
>>>     self.status = status
>>>     # parent exception class is initialized with same number of parameters
>>>     super().__init__(message, status)

D. Beazley and B.K. Jones, Python Cookbook, 3rd Ed. (O'Reilly Media, Sebastopol, CA, May 2013), p. 579